1. Field of the Invention
The present application relates to wireless networking and, in some preferred embodiments, to systems and methods of wireless Quality of Service (QoS) Provisioning through Adaptable and Network Regulated Channel Access Parameters (ANR-CAP) in wireless networks and/or the like.
2. General Background Discussion
Networks and Internet Protocol
There are many types of computer networks, with the Internet having the most notoriety. The Internet is a worldwide network of computer networks. Today, the Internet is a public and self-sustaining network that is available to many millions of users. The Internet uses a set of communication protocols called TCP/IP (i.e., Transmission Control Protocol/Internet Protocol) to connect hosts. The Internet has a communications infrastructure known as the Internet backbone. Access to the Internet backbone is largely controlled by Internet Service Providers (ISPs) that resell access to corporations and individuals.
With respect to IP (Internet Protocol), this is a protocol by which data can be sent from one device (e.g., a phone, a PDA [Personal Digital Assistant], a computers, etc.) to another device on a network. There are a variety of versions of IP today, including, e.g., IPv4, IPv6, etc. Each host device on the network has at least one IP address that is its own unique identifier.
IP is a connectionless protocol. The connection between end points during a communication is not continuous. When a user sends or receives data or messages, the data or messages are divided into components known as packets. Every packet is treated as an independent unit of data.
In order to standardize the transmission between points over the Internet or the like networks, an OSI (Open Systems Interconnection) model was established. The OSI model separates the communications processes between two points in a network into seven stacked layers, with each layer adding its own set of functions. Each device handles a message so that there is a downward flow through each layer at a sending end point and an upward flow through the layers at a receiving end point. The programming and/or hardware that provides the seven layers of function is typically a combination of device operating systems, application software, TCP/IP and/or other transport and network protocols, and other software and hardware.
Typically, the top four layers are used when a message passes from or to a user and the bottom three layers are used when a message passes through a device (e.g., an IP host device). An IP host is any device on the network that is capable of transmitting and receiving IP packets, such as a server, a router, or a workstation. Messages destined for some other host are not passed up to the upper layers but are forwarded to the other host. In the OSI and other similar models, IP is in Layer-3, the network layer.
Wireless Networks:
Wireless networks can incorporate a variety of types of mobile devices, such as, e.g., cellular and wireless telephones, PCs (personal computers), laptop computers, wearable computers, cordless phones, pagers, headsets, printers, PDAs, etc. For example, mobile devices may include digital systems to secure fast wireless transmissions of voice and/or data. Typical mobile devices include some or all of the following components: a transceiver (i.e., a transmitter and a receiver, including, e.g. a single chip transceiver with an integrated transmitter, receiver and, if desired, other functions); an antenna; a processor; one or more audio transducers (for example, a speaker or a microphone as in devices for audio communications); electromagnetic data storage (such as, e.g., ROM, RAM, digital data storage, etc., such as in devices where data processing is provided); memory; flash memory; a full chip set or integrated circuit; interfaces (such as, e.g. USB, CODEC, UART, PCM, etch); and/or the like.
Wireless LANs (WLANs) in which a mobile user can connect to a local area network (LAN) through a wireless connection may be employed for wireless communications. Wireless communications can include, e.g. communications that propagate via electromagnetic waves, such as light, infrared, radio, microwave. There are a variety of WLAN standards that currently exist, such as, e.g., Bluetooth, IEEE 802.11, and HomeRF.
By way of example, Bluetooth products may be used to provide links between mobile computers, mobile phones, portable handheld devices, personal digital assistants (PDAs), and other mobile devices and connectivity to the Internet. Bluetooth is a computing and telecommunications industry specification that details how mobile devices can easily interconnect with each other and with non-mobile devices using a short-range wireless connection. Bluetooth creates a digital wireless protocol to address end-user problems arising from the proliferation of various mobile devices that need to keep data synchronized and consistent from one device to another, thereby allowing equipment from different vendors to work seamlessly together. Bluetooth devices may be named according to a common naming concept. For example, a Bluetooth device may possess a Bluetooth Device Name (BDN) or a name associated with a unique Bluetooth Device Address (BDA). Bluetooth devices may also participate in an Internet Protocol (IP) network. If a Bluetooth device functions on an IP network, it may be provided with an IP address and an IP (network) name. Thus, a Bluetooth Device configured to participate on an IP network may contain, e.g., a BDN, a BDA, an IP address, and an IP name. The term “IP name” refers to a name corresponding to an IP address of an interface.
An IEEE standard, IEEE 802.11, specifies technologies for wireless LANs and devices. Using 802.11, wireless networking may be accomplished with each single base station supporting several devices. In some examples, devices may come pre-equipped with wireless hardware or a user may install a separate piece of hardware, such as a card, that may include an antenna. By way of example, devices used in 802.11 typically include three notable elements, whether or not the device is an access point (AP), a mobile station (STA), a bridge, a PCMCIA card or another device: a radio transceiver; an antenna; and a MAC (Media Access Control) layer that controls packet flow between points in a network.
In addition, Multiple Interface Devices (MIDs) may be utilized in some wireless networks. MIDs may contain two independent network interfaces, such as a Bluetooth interface and an 802.11 interface, thus allowing the MID to participate on two separate networks as well as to interface with Bluetooth devices. The MID may have an IP address and a common IP (network) name associated with the IP address.
Wireless network devices may include, but are not limited to Bluetooth devices, Multiple Interface Devices (MIDs), 802.11x devices (IEEE 802.11 devices including, e.g., 802.11a, 802.11b and 802.11g devices), HomeRF (Home Radio Frequency) devices, Wi-Fi (Wireless Fidelity) devices, GPRS (General Packet Radio Service) devices, 3 G cellular devices, 2.5 G cellular devices, GSM (Global System for Mobile Communications) devices, EDGE (Enhanced Data for GSM Evolution) devices, TDMA type (Time Division Multiple Access) devices, or CDMA type (Code Division Multiple Access) devices, including CDMA2000. Each network device may contain addresses of varying types including but not limited to an IP address, a Bluetooth Device Address, a Bluetooth Common Name, a Bluetooth IP address, a Bluetooth IP Common Name, an 802.11 IP Address, an 802.11 IP common Name, or an IEEE MAC address.
Wireless networks can also involve methods and protocols found in, e.g., Mobile IP (Internet Protocol) systems, in PCS systems, and in other mobile network systems. With respect to Mobile IP, this involves a standard communications protocol created by the Internet Engineering Task Force (IETF). With Mobile IP, mobile device users can move across networks while maintaining their IP Address assigned once. See Request for Comments (RFC) 3344. NB: RFCs are formal documents of the Internet Engineering Task Force (IETF). Mobile IP enhances Internet Protocol (IP) and adds means to forward Internet traffic to mobile devices when connecting outside their home network. Mobile IP assigns each mobile node a home address on its home network and a care-of-address (CoA) that identifies the current location of the device within a network and its subnets. When a device is moved to a different network, it receives a new care-of address. A mobility agent on the home network can associate each home address with its care-of address. The mobile node can send the home agent a binding update each time it changes its care-of address using, e.g., Internet Control Message Protocol (ICMP).
In basic IP routing (i.e. outside mobile IP), typically, routing mechanisms rely on the assumptions that each network node always has a constant attachment point to, e.g., the Internet and that each node's IP address identifies the network link it is attached to. In this document, the terminology “node” includes a connection point, which can include, e.g., a redistribution point or an end point for data transmissions, and which can recognize, process and/or forward communications to other nodes. For example, Internet routers can look at, e.g., an IP address prefix or the like identifying a device's network. Then, at a network level, routers can look at, e.g., a set of bits identifying a particular subnet. Then, at a subnet level, routers can look at, e.g., a set of bits identifying a particular device. With typical mobile IP communications, if a user disconnects a mobile device from, e.g., the Internet and tries to reconnect it at a new subnet, then the device has to be reconfigured with a new IP address, a proper netmask and a default router. Otherwise, routing protocols would not be able to deliver the packets properly.
Wireless networks are expected to support different Quality of Service (QoS) classes of traffic that have diverse bandwidth, delay, and packet loss requirements. These QoS classes may range from e.g., E-mails to realtime multimedia services. The most critical layers to support different QoS classes are Physical, Medium Access Control (MAC), and Network. Though the Wire-Line part of the network, particularly if it equipped with optical fiber, can meet the future bandwidth needs, the wireless part of the network presents a bottleneck in delivery of bandwidth hungry time sensitive applications because bandwidth is a scarce resource. This calls for introduction of layer 2 prioritized delivery mechanisms for different traffic classes for service differentiation and QoS provisioning.
The IEEE 802.11e task group enhanced the current 802.11 MAC and interrelated protocol efficiency to expand support for applications with QoS requirements. This effort involved usage of different sets of Channel Access Parameters (CAP) for different classes. The CAP includes Arbitration Inter-Frame Spaces (AIFS) and Contention Windows (CW). Though CAP (i.e., AIFS and CW) differentiation provides superior and more robust operation it institutes several performance issues. For example it does not consider the adaptability of CAP values duly tailored with the prevailing load conditions. Moreover it restricts the set of CAP for each Access Category (AC), per Mobile Node (MN), rather than per AC. Furthermore it does not consider the fact that some Mobile Nodes (MNs) may claim false priorities, set their CAP to the highest priority (small AIFS, small CW etc.), and enjoy priority treatment that they might not deserve because they might not be actually running time sensitive applications. Under this situation the network is handicapped to assess authenticity of MNs priority claim and hence cannot do anything except to trust MNs and keep providing them the differentiated treatment.
A lot of work has been done to provide guaranteed QoS for enhanced user experience. However, guaranteed QoS is not easily achievable in Packet Switched Networks as compared to Circuit Switched Networks. The difference is due to the fact that Circuit Switched Networks provide dedicated links for each connection while Packet Switched Networks do not. Furthermore when the Undedicated Packet Switched Networks are bridged over “Wireless” (specifically IEEE 802.11 WLANs), the promise of QoS becomes a little more difficult because all MNs share the access to the same radio channel. In addition to these anomalies, when these networks are required to serve delay sensitive, packet loss intolerant, or bandwidth hungry multimedia applications, QoS guarantee becomes more challenging because the number of users demanding multimedia applications may be erratic. Thus, the service differentiation mechanisms must be compulsorily introduced at the MAC layer. The IEEE 802.1 le task group, chartered to introduce QoS support at the MAC layer, strived to enhance current MAC and associated protocols so that the applications demanding differentiated treatment can be supported efficiently. The current 802.1 le draft standard defines two mechanisms, enhanced distributed channel access (EDCA), and hybrid coordination function (HCF) controlled channel access (HCCA), both of which are backward compatible with the legacy distributed coordination function (DCF) access mechanism defined by the 1999 standard [1].
EDCA
According to 802.1 le's EDCA approach, user applications are classified into four classes or Access Categories (AC) for differential treatment. These ACs are in line with those defined by 3GPP and are given below:
1) AC-Back Ground (AC-BG);
2) AC-Best Effort (AC-BE);
3) AC-Video (AC-VI); and
4) AC-Voice (AC-VO).
AC-BG and AG-BE are referred as Background and Interactive Traffic Classes. They carry Non-Real-Time Traffic, i.e., traditional Internet applications, e.g., web browsing, telnet, email, and FTP.). AC-VI and AC-VO stand for Vldeo and Voice, and are also referred to as Streaming/Conversational Classes. They carry Real-Time Traffic flows.
Packets arriving at the MAC (MSDUs) are mapped into the foregoing four ACs that represent four different levels of service in contention for the shared medium. Each AC contends for the medium with the same rules as the standard DCF (i.e., wait until the channel is idle for a given amount of Interframe Space (IFS) and then access/retry following exponential back-off rules). The access probability differentiation for different ACs is provided by using different sets of Channel Access Parameters referred to as CW Differentiation and AIFS Differentiation.
CW Differentiation; CW differentiation refers to the back-off times through different settings of the CWmin and CWmax parameters per above noted class. EDCF uses the contention window to assign priority to each AC. Indeed, assigning a short contention window to a high priority AC ensures that in most cases, high priority AC is able to transmit ahead of low priority one. Thus, the CWmin and CWmax parameters can be set differently for different access categories, such as, a high priority AC with small values of CWmin and CWmax. Moreover CW differentiation can be used to differentiate users within the same AC.
AFPS Differentiation: The AIFS (Arbitration InterFrame Space) refers to the amount of time a MN defers access to the channel following a busy channel period, i.e., after every busy channel period, each MN waits for a time equal to its AIFS value. EDCA proposes using different AIFS values for different access categories (AC) instead of the constant distributed IFS (DIFS) used in DCF. Thus the flows with shorter AIFS values may access the channel, while the flows with longer AIFS values are prevented from accessing the channel. Once an AIFS has elapsed, the MN access is managed by the normal back-off rules. AIFS values differ for an integer number of slot times. This implies that the channel access can be still considered slotted, and MNs may access the channel only at the discrete time instants. The typical values of AIFS are 7, 3, 2 and 2 for above noted four classes.
CW and AFIS in this document are referred as Channel Access Parameters, abbreviated as CAP. Though CAP differentiation approach of EDCA provides superior performance, however, it presents several drawbacks as well as gaps in the standard that need to be filled, e.g.
1. It trusts the MNs to select CAP for themselves and ignores the fact that MNs can falsely set its traffic parameters to the highest priority (small AIFS and small CWmin). And if all the MNs set the highest priorities, the spirit of the concept dies.
2. There are fixed default values of AP for each AC (i.e., greater AIFS and CWmin for AC-BK, AC-BE, and smaller AFIS and CWmin for AC-VI, AC-VO) regardless of the prevailing loading conditions. In case of light loading condition this may be a less critical problem, however in case of heavily loaded condition, the obvious drawback would be that smaller CWmin values would lead to smaller aggregate throughput, or higher delay that would adversely impact the acceptable QoS. This is because reduction of the CWmin value during congestion may significantly increase the probability of collision on the channel, thus reducing the overall effectiveness of the mechanism.